Marijuana grown indoors using a hydroponics system (tubes and filters with water and fertilizers). To correct the first definition, NO marijuana causes mental problems - but it does get you really high.

I couldn't find any hydro for the weekend, so I had to settle for some reg.

hydro ( a.k.a hydroponic ) is a high grade marijuana. It is grown by using hydroponics ( hense the name hyrdo ). Hydroponics is an alternitive to growing the seeds in dirt. It is usually grown in water just like lilly pads grow.